PROJECT SUMMARY Pain management in craniofacial pathology is a major clinical challenge. Thorough understanding of the molecular mechanisms underlying craniofacial pain should help the development of novel strategies for better treatment. TRPV1 is a receptor for capsaicin and multiple endogenous stimuli such as heat and proton. In addition to its well-known contribution to thermal hyperalgesia, TRPV1 also integrates nociceptive signaling under inflammation and injury, and is implicated in various craniofacial pathological conditions. Although TRPV1 is a good candidate for craniofacial anti-hyperalgesic therapy, antagonists that suppress TRPV1 function completely may not be applicable due to serious adverse side effects. Therefore, it will be important to develop therapeutics targeting pathology-specific TRPV1 activity. Based on the literature and our preliminary data, we hypothesize that alteration in activity of TRPV1 mediated by post-translational modification and genetic variations contributes to craniofacial pathological pain. To test this hypothesis, we will perform a comprehensive analysis in vitro, in vivo and in humans. We will determine modality-specific basis for the phosphorylation-induced hypersensitivity of TRPV1 (Aim 1), examine the contribution of PKC-induced phosphorylation of TRPV1 to hypersensitivity in sensory neurons and to craniofacial pain in vivo (Aim 2), and determine whether nonsynonymous variations within the human TRPV1 locus induce coupled alterations of channel functions in vitro and craniofacial pain phenotypes in humans (Aim 3). If successful, this project will provide information that guides development of novel approaches for targeting pathology-specific residues of TRPV1 and/or selective patient subgroups for treating craniofacial pain.